Prediction model for condensation of binary refrigerant mixtures inside a horizontal smooth tube

In the present study, a prediction model for condensation of binary refrigerant mixtures inside a horizontal smooth tube is proposed. In this model it is assumed that the phase equilibrium is only established at the vapor-liquid interface, while the bulk vapor and the bulk liquid are in a nonequilibrium state. The predicted results are compared with the experimental ones for the condensation of HFC134a/HCFC123 mixtures; in the experiment, the bulk mass fraction of HFC134a ranged from 0.35 to 0.85 kg/kg, and the mass velocity of 120 to 300 kg/(m²s). Since the mass transfer characteristics in the vapor core are assumed to be expressed as Sh_v = 0.046 Re_v^0.8Sc_v^0.3, the predicted heat flux distribution along the tube axis is in good agreement with that of the experiment. The mass transfer characteristics during the condensation, determined by the prediction calculation, are also presented.